Device and method for producing moulded bodies from thermoplastic polymers

ABSTRACT

An apparatus suitable for producing shaped bodies comprising thermoplastic polymers from monomers which form such polymers in a batch process comprises a) at least one reactor suitable for the batchwise preparation of a melt of a thermoplastic polymer from monomers which form such a polymer, b) a piping system suitable as circulation line for the melt of the thermoplastic polymer and c) at least one apparatus suitable for the production of shaped bodies from the melt of a thermoplastic polymer, wherein the reactor or reactors a) is/are connected to the piping system b) and the apparatus or apparatuses c) is/are connected to the piping system b), and an apparatus for producing shaped bodies comprising thermoplastic polymers in such an apparatus.

The present invention relates to an apparatus and a process forproducing shaped bodies comprising thermoplastic polymers with batchwisepreparation of the thermoplastic polymers from monomers which form suchthermoplastic polymers.

For the purposes of the present invention, thermoplastic polymers arepolymers which have a melting point in accordance with ISO 11357-1 and11357-3.

Processes for the batchwise preparation of thermoplastic polymers frommonomers which form such thermoplastic polymers are generally known.

Thus, Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., Vol.19, John Wiley & Sons, New York, 1996, pages 491-492 (bridgingparagraph), or Fourné, Synthetische Fasern, Carl Hanser Verlag,Munich/Vienna, 1995, page 58, describe the preparation of polyamide 66(nylon 66) from hexamethylenediammonium adipate in a batch process in anautoclave.

Fourné, Synthetische Fasern, loc cit, pages 46-47, discloses thepreparation of polyamide 6 (nylon 6) from caprolactam in a batch processin an autoclave.

In both cases, the result is a melt of the corresponding thermoplasticpolymer which is taken from the autoclave and usually fed directly intoan apparatus for the production of shaped bodies, e.g. granules, fromthe polymer.

Since the polymer is prepared batchwise and the melt is therefore alsotaken from the autoclave discontinuously, the apparatus for theproduction of shaped bodies has to be started up when the melt is takenfrom the autoclave and shut down again afterwards. A disadvantage isthat large amounts of off-specification product, in particular producthaving a brownish discoloration due to decomposition of the polymer, areobtained both during the start-up phase and also during the shutdownphase.

In addition, the apparatus for producing the shaped bodies is idleduring the polymerization time.

It is well known that the time required for preparing the polymer meltfrom the monomers is very long compared to the time for taking off thepolymer melt. According to Fourné, loc cit, pages 58-59, in the case ofnylon 66 the total cycle time is about 7 hours and the time for takingoff the melt is about 10 minutes and in the case of nylon 6, accordingto Fourné, loc cit, page 47, the preparation time is about 23 hours andthe time for taking off the melt is about 60 minutes; if the apparatusfor producing shaped bodies from the polymer is linked in a fixed mannerwith the autoclave concerned, the abovementioned times imply autilization time for the appratus for producing the shaped bodies ofabout 4% in the case of nylon 6 and about 2.4% in the case of nylon 66.

It is known from Fourné, loc cit, page 47, that the apparatus forproducing the shaped bodies can be constructed so as to be able to bemoved among many autoclaves in order to avoid this disadvantage. Thismeans that the apparatus can be moved from autoclave to autoclave, forexample on rails. The apparatus is in each case pushed under theautoclave which is available for emptying and connected to thisautoclave. The melt is then discharged from the autoclave into theapparatus and the shaped bodies are produced. After all the polymer hasbeen taken from the autoclave, the apparatus is once again disconnectedfrom the autoclave and pushed under the next autoclave available foremptying.

In this way, the utilization time of the apparatus can be increased, butthis procedure is labor-intensive. In addition, the ability to move theapparatus does not solve the problem of the continual cyclic start-upand shutdown of the apparatus and the associated disadvantages describedabove.

To solve the problem associated with the continual cyclic start-up andshutdown of the apparatus, it has been proposed that the autoclavesfirstly be emptied into a reservoir and the apparatus for producing theshaped bodies be supplied continuously from this reservoir.

In this case, it has been observed that deposits of decompositionproducts are formed in the reservoir, particularly in the upper regionof the melt, due to the continual changes in level in the reservoir.

This is in agreement with Fourné, loc cit, page 47, 58-59, in particularpage 61, according to whom the polymer melts are thermally unstable andthis instability requires very short and uniform residence times, i.e.short melt lines having a small volume. A reservoir is diametricallyopposed to these requirements.

It is an object of the present invention to provide an apparatus and aprocess which make it possible to prepare shaped bodies comprisingthermoplastic polymers with batchwise preparation of the thermoplasticpolymers from monomers which form such thermoplastic polymers whileavoiding the above-mentioned disadvantages.

We have found that this object is achieved by an apparatus suitable forproducing shaped bodies comprising thermoplastic polymers from monomerswhich form such polymers in a batch process, comprising

-   a) at least one reactor suitable for the batchwise preparation of a    melt of a thermoplastic polymer from monomers which form such a    polymer,-   b) a piping system suitable as circulation line for the melt of the    thermoplastic polymer and-   c) at least one apparatus suitable for the production of shaped    bodies from the melt of a thermoplastic polymer,    wherein-   the reactor or reactors a) is/are connected to the piping system b)    and-   the apparatus or apparatuses c) is/are connected to the piping    system b),    and an apparatus for producing shaped bodies comprising    thermoplastic polymers from monomers which form such polymers in a    batch process in such an apparatus, which comprises-   a) preparing a melt of a thermoplastic polymer batchwise from    monomers which form such a polymer in at least one reactor,-   b) feeding the melt of the thermoplastic polymer obtained in step a)    into a piping system suitable as circulation line for the melt of    the thermoplastic polymer and moving it through the piping system at    a mean average wall shear rate in the range from 0.1 to 100 s-¹ and    a mean average flow velocity in the range from 0.1 to 100 cm/s,-   c) taking the melt of the thermoplastic polymer from the piping    system b) and producing shaped bodies from the thermoplastic    polymer.

According to the present invention, the apparatus comprises at least onereactor suitable for the batchwise preparation of a melt of athermoplastic polymer from monomers which form such a polymer.

If the apparatus comprises one such reactor, the apparatus of thepresent invention enables, in particular, the formation of deposits inlines which connect the reactor to at least one apparatus suitable forproducing shaped bodies from the melt of a thermoplastic polymer to beeffectively avoided.

If the apparatus comprises more than one reactor, for example 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 reactors,preferably 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 reactors, the apparatus ofthe present invention enables, in particular, the formation of depositsin lines which connect the reactor to at least one apparatus suitablefor producing shaped bodies from the melt of a thermoplastic polymer tobe effectively avoided.

In addition, operation of the reactors or groups of reactors canadvantageously be staggered over time, in particular in such a way thatthe thermoplastic polymers are prepared in one reactor or a group ofreactors, thermoplastic polymer is taken from another reactor or anothergroup of reactors and, if appropriate, a further reactor or a furthergroup of reactors is filled, and the functions of the reactors or groupsof reactors are then rotated. In this way, continuous introduction ofthermoplastic polymer into the piping system b) which is suitable ascirculation line can be achieved in a particularly advantageous manner.Likewise, continuous tapping of thermoplastic polymer from the pipingsystem b) which is suitable as circulation line can in this way beachieved in a particularly advantageous manner.

According to the present invention, the reactor a) is suitable forpreparing a melt of a thermoplastic polymer. For the purposes of thepresent invention, a thermoplastic polymer is a polymer which has amelting point which can be determined in accordance with ISO 11357-1 and11357-3.

Possible thermoplastic polymers are polymers which have functionalgroups in the main polymer chain or ones which have no functional groupsin the main polymer chain, e.g. polyolefins such as polyethylene,polypropylene, polyisobutylene. The preparation of such polyolefins isknown per se, for example from: Kirk-Othmer, Encyclopedia of ChemicalTechnology, 4th Ed., Vol. 17, John Wiley & Sons, New York, 1996, pages705-839, or Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed.,Vol. A21, VCH Verlagsgesellschaft mbH, Weinheim, 1992, pages 487-577.

In a preferred embodiment, the thermoplastic polymer used can be apolymer whose main polymer chain comprises at least one recurringfunctional group of the structure—(R¹)_(x)—C(O)—(R²)_(y)—where

-   x, y: are each, independently of one another, 0 or 1, where x+y=1-   R¹, R²: are each, independently of one another, oxygen or nitrogen    bound into the main polymer chain, where two bonds of the nitrogen    can advantageously be linked to the polymer chain and the third bond    can bear a substituent selected from the group consisting of    hydrogen, alkyl, preferably C₁-C₁₀-alkyl, in particular C₁-C₄-alkyl,    e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl,    aryl, heteroaryl and —C(O)—, where the group —C(O)— may bear a    further polymer chain, alkyl, preferably C₁-C₁₀-alkyl, in particular    C₁-C₄-alkyl, e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl,    i-butyl, s-butyl, aryl, heteroaryl,-   for example —N—C(O)—, —C(O)—N—, —O—C(O)—, —C(O)—O— or mixtures    thereof, in particular —N—C(O)— or —C(O)—N— or their mixtures. In    the case of —N—C(O)— or —C(O)—N— or their mixtures, the    thermoplastic polymer is a polyamide.

For the purposes of the present invention, polyamides are homopolymers,copolymers, blends and grafted polymers comprising synthetic long-chainpolyamides whose defining constituent is a recurring amide group in themain polymer chain. Examples of such polyamides are nylon 6(polycaprolactam), nylon 6.6 (polyhexamethyleneadipamide), nylon 4.6(polytetramethyleneadipamide), nylon 6.10 (polyhexamethylenesebacamide),nylon 7 (polyenantholactam), nylon 11 (polyundecanolactam), nylon 12(polydodecanolactam). These polyamides are known by the generic name ofnylon. Polyamides also include aramids (aromatic polyamides), e.g.polymetaphenyleneisophthalamide (NOMEX® fiber, U.S. Pat. No. 3,287,324)or polyparaphenyleneterephthalamide (KEVLAR® fiber, U.S. Pat. No.3,671,542).

Polyamides can be produced by two principal methods.

Both in the polymerization from dicarboxylic acids and diamines and inthe polymerization from amino acids or their derivatives such asaminocarboxylic nitriles, aminocarboxamides, aminocarboxylic esters orsalts of aminocarboxylic acids, the amino and carboxyl end groups of thestarting monomers or starting oligomers react with one another to forman amide group and water. The water can subsequently be removed from thepolymer mass. In the polymerization from carboxamides, the amino andamide end groups of the starting monomers or starting oligomers reactwith one another to form an amide group and ammonia. The ammonia cansubsequently be removed from the polymer mass. This polymerizationreaction is usually referred to as polycondensation.

The polymerization from lactams as starting monomers or startingoligomers is usually referred to as polyaddition.

Such polyamides can be obtained from monomers selected from the groupconsisting of lactams, omega-aminocarboxylic acids,omega-aminocarboxylic nitriles, omega-aminocarboxamides, salts ofomega-aminocarboxylic acids, omega-aminocarboxylic esters, equimolarmixtures of diamines and dicarboxylic acids, dicarboxylic acid/diaminesalts, dinitriles and diamines or mixtures of such monomers by methodsknown per se, as are described, for example, in DE-A-14 95 198, DE-A-2558 480, EP-A-129 196 or in: Polymerization Processes, Interscience, NewYork, 1977, pp. 424-467, in particular pp. 444-446.

Possible monomers are:

-   monomers or oligomers of a C₂₋C₂₀₋, preferably C₂₋C₁₈-arylaliphatic    or preferably aliphatic lactam, e.g. enantholactam, undecanolactam,    dodecanolactam or caprolactam,-   monomers or oligomers of C₂₋C₂₀₋, preferably C₃₋C₁₈-aminocarboxylic    acids, e.g. 6-aminocaproic acid, 11-aminoundecanoic acid, and also    their dimers, trimers, tetramers, pentamers and hexamers, and also    their salts such as alkali metal salts, for example lithium, sodium,    potassium salts,-   C₂₋C₂₀₋, preferably C₃₋C₁₈-aminocarboxylic nitriles, e.g.    6-aminocapronitrile, 11-aminoundecanenitrile,-   monomers or oligomers of C₂₋C₂₀-amino acid amides, e.g.    6-aminocaproamide, 11-aminoundecanoamide and also their dimers,    trimers, tetramers, pentamers or hexamers,-   esters, preferably C₁-C₄-alkyl esters, e.g. methyl, ethyl, n-propyl,    i-propyl, n-butyl, i-butyl, s-butyl esters, of C₂₋C₂₀₋, preferably    C₃₋C₁₈-aminocarboxylic acids, e.g. 6-aminocaproic esters, for    example methyl 6-aminocaproate, 11-aminoundecanoic esters, for    example methyl 11-aminoundecanoate,-   monomers or oligomers of a C₂₋C₂₀₋, preferably    C₂₋C₁₂-alkylenediamine, e.g. tetramethylenediamine or preferably    hexamethylenediamine, with a C₂₋C₂₀, preferably C₂₋C₁₄ aliphatic    dicarboxylic acid or a mononitrile or dinitrile thereof, e.g.    sebacic acid, dodecanedioic acid, adipic acid, sebaconitrile,    decanedinitrile or adiponitrile, and also their dimers, trimers,    tetramers, pentamers or hexamers,-   monomers or oligomers of a C₂₋C₂₀, preferably    C₂₋C₁₂-alkylenediamine, e.g. tetramethylenediamine or preferably    hexamethylenediamine, with a C₈₋C₂₀, preferably C₈₋C₁₂ aromatic    dicarboxylic acid or a derivative thereof, for example an acid    chloride, e.g. 2,6-naphthalenedicarboxylic acid, preferably    isophthalic acid or terephthalic acid, and also their dimers,    trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₂₋C₂₀, preferably    C₂₋C₁₂-alkylenediamine, e.g. tetramethylenediamine or preferably    hexamethylenediamine, with a C₉₋C₂₀, preferably C₉₋C₁₈-arylaliphatic    dicarboxylic acid or a derivative thereof, for example an acid    chloride, e.g. o-, m- or p-phenylenediacetic acid, and also their    dimers, trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₆₋C₂₀, preferably C₆₋C₁₀ aromatic    diamine, e.g. m- or p-phenylenediamine, with a C₂₋C₂₀, preferably    C₂₋C₁₄ aliphatic dicarboxylic acid or a mononitrile or dinitrile    thereof, e.g. sebacic acid, dodecanedioic acid, adipic acid,    sebaconitrile, decanedinitrile or adiponitrile, and also their    dimers, trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₆₋C₂₀, preferably C₆₋C₁₀ aromatic    diamine, e.g. m- or p-phenylenediamine, with a C₈₋C₂₀, preferably    C₈₋C₁₂ aromatic dicarboxylic acid or a derivative thereof, for    example an acid chloride, e.g. 2,6-naphthalenedicarboxylic acid,    preferably isophthalic acid or terephthalic acid, and also their    dimers, trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₆₋C₂₀, preferably C₆₋C₁₀ aromatic    diamine, e.g. m- or p-phenylenediamine, with a C₉₋C₂₀, preferably    C₉₋C₁₈ arylaliphatic dicarboxylic acid or a derivative thereof, for    example an acid chloride, e.g. o-, m- or p-phenylenediacetic acid,    and also their dimers, trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₇₋C₂₀, preferably C₈₋C₁₈ arylaliphatic    diamine, e.g. m- or p-xylylenediamine, with a C₂₋C₂₀, preferably    C₂₋C₁₄ aliphatic dicarboxylic acid or a mononitrile or dinitrile    thereof, e.g. sebacic acid, dodecanedioic acid, adipic acid,    sebaconitrile, decanedinitrile or adiponitrile, and also their    dimers, trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₇₋C₂₀, preferably C₈₋C₁₈ arylaliphatic    diamine, e.g. m- or p-xylylenediamine, with a C₆₋C₂₀, preferably    C₆₋C₁₀ aromatic dicarboxylic acid or a derivative thereof, for    example an acid chloride, e.g. 2,6-naphthalenedicarboxylic acid,    preferably isophthalic acid or terephthalic acid, and also their    dimers, trimers, tetramers, pentamers or hexamers,-   monomers or oligomers of a C₇₋C₂₀, preferably C₈₋C₁₈ arylaliphatic    diamine, e.g. m- or p-xylylenediamine, with a C₉₋C₂₀, preferably    C₉₋C₁₈ arylaliphatic dicarboxylic acid or a derivative thereof, for    example an acid chloride, e.g. o-, m- or p-phenylenediacetic acid,    and also their dimers, trimers, tetramers, pentamers or hexamers,    and also homopolymers, copolymers, mixtures and grafted polymers of    such starting monomers or starting oligomers.

In a preferred embodiment, caprolactam is used as lactam,tetramethylenediamine, hexamethylenediamine, m-xylylenediamine,p-xylylenediamine or a mixture thereof is used as diamine and adipicacid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalicacid or a mixture thereof is used as dicarboxylic acid. Particularpreference is given to caprolactam as lactam, hexamethylenediamine orm-xylylenediamine as diamine and adipic or terephthalic acid asdicarboxylic acid, or a mixture thereof, in particularhexamethylenediammonium adipate.

Particular preference is given to starting monomers or startingoligomers which on polymerization lead to the polyamides nylon 6, nylon6.6, nylon 4.6, nylon 6.10, nylon 6.12, nylon 7, nylon 11, nylon 12,poly-m-xylyleneadipamide or the aramids polymetaphenyleneisophthalamideor poly-paraphenyleneterephthalamide, in particular to nylon 6 or nylon6.6, particularly preferably nylon 6.6.

In a preferred embodiment, one or more chain regulators can be used inthe preparation of the polyamides. Advantageous chain regulators arecompounds which have two, three or four, in the case of systems in theform of fibers preferably two, amino groups which are reactive inpolyamide formation or one or more, e.g. two, three or four, in the caseof systems in the form of fibers preferably two, carboxyl groups whichare reactive in polyamide formation.

In the first case, the products obtained are polyamides where themonomers used for preparing the polyamide have a greater number of aminegroups or their equivalents used to form the polymer chain than carboxylgroups or their equivalents used to form the polymer chain.

In the second case, the products obtained are polyamides where themonomers used for preparing the polyamide have a greater number ofcarboxyl groups or their equivalents used to form the polymer chain thanamine groups or their equivalents used to form the polymer chain.

Compounds which can advantageously be used as chain regulators aremonocarboxylic acids such as alkanecarboxylic acids, preferably havingfrom 1 to 20 carbon atoms including the carboxyl group, for exampleacetic acid or propionic acid, benzenemonocarboxylic ornaphthalenemonocarboxylic acids, for example benzoic acid, dicarboxylicacids such as C₄-C₁₀-alkanedicarboxylic acids, for example adipic acid,azelaic acid, sebacic acid, dodecanedioic acid,C₅-C₈-cycloalkanedicarboxylic acids, for examplecyclohexane-1,4-dicarboxylic acid, benzene or naphthalenedicarboxylicacids, for example terephthalic acid, isophthalic acid,naphthalene-2,6-dicarboxylic acid, C₂₋C₂₀-, preferablyC₂₋C₁₂-alkylamines, e.g. cyclohexylamine, C₆₋C₂₀, preferably C₆₋C₁₀aromatic monoamines, e.g. aniline, or C₇₋C₂₀, preferably C₈₋C₁₈arylaliphatic monoamines, e.g. benzylamine, diamines, such asC₄-C₁₀-alkanediamines, for example hexamethylenediamine.

The chain regulators can be unsubstituted or substituted, for example byaliphatic groups, preferably C₁-C₈-alkyl groups such as methyl, ethyl,i-propyl, n-propyl, n-butyl, i-butyl, s-butyl, n-pentyl, n-hexyl,n-heptyl, n-octyl, 2-ethylhexyl, OH, ═O, C₁-C₈-alkoxy, COOH,C₂-C₆-carbalkoxy, C₁-C₁₀-acyloxy or C₁-C₈-alkylamino, sulfonic acids ortheir salts, e.g. alkali metal or alkaline earth metal salts, cyano orhalogens such as fluorine, chlorine, bromine. Examples of substitutedchain regulators are sulfoisophthalic acid, its alkali metal or alkalineearth metal salts, e.g. lithium, sodium or potassium salts,sulfoisophthalic esters, for example esters with C₁-C₁₆-alkanols, orsulfoisophthalic monoamides or diamides, in particular with monomerswhich bear at least one amine group and are suitable for formingpolyamides, e.g. hexamethylenediamine or 6-aminocaproic acid.

A chain regulator can advantageously be used in amounts of at least 0.01mol %, preferably at least 0.05 mol %, in particular at least 0.2 mol %,based on 1 mol of acid amide groups of the polyamide.

A chain regulator can advantageously be used in amounts of not more than1.0 mol %, preferably not more than 0.6 mol %, in particular not morethan 0.5 mol %, based on 1 mol of acid amide groups of the polyamide.

In an advantageous embodiment, the polyamide can comprise a stericallyhindered piperidine derivative which is chemically bound to the polymerchain as chain regulator. In this case, a single sterically hinderedpiperidine derivative or a mixture of such sterically hinderedpiperidine derivatives can be present in the polyamide.

As sterically hindered piperidine derivative, preference is given tocompounds of the formula

where

-   R¹ is a functional group which is capable of amide formation with    the polymer chain of the polyamide,    -   preferably an —(NH)R⁵ group, where R⁵ is hydrogen or        C₁-C₈-alkyl, or a carboxyl group or a carboxyl derivative or a        —(CH₂)_(x)(NH)R⁵ group, where x is from 1 to 6 and R⁵ is        hydrogen or C₁-C₈-alkyl, or a —(CH₂)_(y)COOH group, where y is        from 1 to 6, or a —(CH₂)_(y)COOH acid derivative, where y is        from 1 to 6, in particular an —NH₂ group,-   R² is an alkyl group, preferably a C₁-C₄-alkyl group such as methyl,    ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, in particular    a methyl group,-   R³ is hydrogen, C₁-C₄-alkyl or O—R⁴, where R⁴ is hydrogen    C₁-C₇-alkyl,    -   in particular hydrogen.

In such compounds, the tertiary or in particular secondary amine groupsof the piperidine ring systems usually do not react because of sterichindrance.

A particularly preferred sterically hindered piperidine derivative is4-amino-2,2,6,6-tetramethylpiperidine.

The sterically hindered piperidine derivative can advantageously be usedin amounts of at least 0.01 mol %, preferably at least 0.05 mol %, inparticular at least 0.1 mol %, based on 1 mol of acid amide groups ofthe polyamide.

The sterically hindered piperidine derivative can advantageously be usedin amounts of not more than 0.8 mol %, preferably not more than 0.6 mol%, in particular not more than 0.4 mol %, based on 1 mol of acid amidegroups of the polyamide.

The polymerization or polycondensation by the process of the presentinvention can be carried out in the presence of at least one pigment.Preferred pigments are titanium dioxide, preferably in the anatasemodification, or color-imparting inorganic or organic compounds. Thepigments are preferably used in an amount of from 0 to 5 parts byweight, in particular from 0.02 to 2 parts by weight, in each case basedon 100 parts by weight of polyamide. The pigments can be fed into thereactor together with the starting materials or separately therefrom.

The polyamide can further comprise organic or inorganic stabilizers, butis preferably free of such stabilizers.

Advantageous thermoplastic polyamides in which a sterically hinderedpiperidine derivative which is chemically bound to the polymer chain ispresent and processes for preparing such polyamides are described, forexample, in WO 95/28443, WO 97/05189, WO 98/50610, WO 99/46323, WO99/48949, EP-A-822 275, EP-A-843 696 and the German patent applications10030515.6, 10030512.1 and 10058291.5.

Reactors for the batchwise preparation of such thermoplastic polyamidesfrom monomers forming such polyamides and also the parameters customaryfor this purpose, e.g. pressure, temperature and content of additivessuch as water, are generally known, for example from Fourné, loc cit,pages 46-47, section 2.2.3.5., and 58-60, section 2.2.4.2., whosecontents are hereby incorporated by reference into the presentdescription.

The preparation of the polymer in step a) can be carried out at apressure above ambient pressure, at ambient pressure or at a pressurebelow ambient pressure (“vacuum polymerization”).

A pressure of not more than 3 MPa, preferably not more than 2.5 MPa, inparticular not more than 20 MPa, has been found to be particularlyadvantageous for the preparation of the polymer in a).

In vacuum polymerization, the lower limit for the pressure is generallyset by the vapor pressure of the reaction mixture under the reactionconditions, e.g. at the respective temperature and composition of thereaction mixture.

A pressure of at least 0.01 MPa (absolute), preferably at least 0.1 MPa(corresponding to ambient pressure), has been found to be particularlyadvantageous for the preparation of the polymer in a). Furthermore, atemperature in the range from 100 to 380° C., preferably from 120 to350° C., in particular from 145 to 295° C., is advantageous for thepreparation of the polymer.

As reactors, pressure-rated vessels, e.g. autoclaves, have been found tobe advantageous. Such vessels may contain devices which promote mixingof the charge in the reactor, e.g. wall stirrers, blade stirrers,turbines, static mixers, injectors.

According to the present invention, a melt of the thermoplastic polymerformed in a) is transferred into a piping system suitable as circulationsystem for the melt of the thermoplastic polymer, for example via apipe.

Here, a very short connection between a) and b) has been found to beparticularly advantageous.

The piping system can comprise a single pipe which forms a circuit or aplurality of such pipes. It is likewise possible for at least one pipeto have a branch so that the melt flows through varying number of pipesduring circulation.

In an advantageous embodiment, the mean average pipe diameter in thepiping system b) between the first reactor a) and the last apparatus c)viewed in the flow direction can be equal to or greater than the meanaverage pipe diameter between the last apparatus c) and the firstreactor a) viewed in the flow direction. In the piping system b), theratio of the mean average pipe diameter between the first reactor a) andthe last apparatus c) viewed in the flow direction to the mean averagepipe diameter between the last apparatus c) and the first reactor a)viewed in the flow direction is preferably in the range from 1:1 to10:1, in particular in the range from 1:1 to 5:1.

According to the present invention, the melt of the thermoplasticpolymer obtained in step a) travels along in the piping system b) at amean average wall shear rate in the range from 0.1 to 100 s-¹,preferably from 0.4 to 50 s-¹, in particular from 1 to 10 s-¹, where thewall shear rate is determined according to the equationdv/dr=(4*V)/(π*r ³)where:

-   -   v: flow velocity    -   V: flow volume    -   r: radius        and at a mean average flow velocity in the range from 0.1 to 100        cm/s, preferably from 0.4 to 50 cm/s, in particular from 1 to 10        cm/s.

The temperature of the melt of the thermoplastic polymer in the pipingsystem is advantageously at least 0° C., preferably at least 10° C.,above the melting point of the thermoplastic polymer, determined inaccordance with ISO 11357-1 and 11357-3.

The temperature of the melt of the thermoplastic polymer in the pipingsystem is advantageously not more than 60° C., preferably not more than40° C., above the melting point of the thermoplastic polymer, determinedin accordance with ISO 11357-1 and 11357-3. The movement of the melt ofthe thermoplastic polymer in the piping system can be generated purelythermally by means of different temperatures and thus densitydifferences in the melt in the piping system.

It has been found to be advantageous for the piping system toadditionally have one or more conveying devices suitable for moving themelt of the thermoplastic polymer in the longitudinal direction of thepiping system, preferably one or more pumps such as gear pumps, wormpumps, screw pumps, disk pumps, extruders, piston pumps, centrifugalpumps.

Particularly advantageous conveying devices and the parameters suitablefor achieving the average mean shear rate and the mean average flowvelocity prescribed according to the present invention can easily bedetermined by means of a few simple preliminary tests.

Furthermore, it has been found to be advantageous for the piping systemto additionally have one or more filtration devices in b). In the caseof a filtration device and a conveying device, it is possible for thefiltration device to be located downstream (based on the direction offlow of the melt) of the conveying device, but is preferably locatedupstream of the conveying device.

Here, the filtration devices known per se for the filtration of polymermelts can be used in a customary manner. Particularly advantageousfiltration devices can easily be determined by means of a few simplepreliminary tests.

According to the present invention, the apparatus comprises at least oneapparatus which is suitable for the production of shaped bodies from themelt of the thermoplastic polymer and is connected to the piping systemb), preferably via a pipe.

It has been found to be particularly advantageous to keep the connectionbetween c) and b) very short.

It has been found to be advantageous for the apparatus of the presentinvention to additionally have one or more conveying devices suitablefor moving the melt of the thermoplastic polymer from b) to c),preferably one or more pumps such as gear pumps, worm pumps, screwpumps, disk pumps, extruders, piston pumps, centrifugal pumps.

Particularly advantageous conveying devices can easily be determined bymeans of a few simple preliminary tests.

Furthermore, it has been found to be advantageous for the apparatus ofthe present invention to additionally have one or more filtrationdevices between b) and c). In the case of a filtration device and aconveying device between b) and c), the filtration device can be locatedupstream (based on the direction of flow of the melt) of the conveyingdevice, but is preferably located downstream of the conveying device.

Here, the filtration devices known per se for the filtration of polymermelts can be used in a customary manner. Particularly advantageousfiltration devices can easily be determined by means of a few simplepreliminary tests.

For the purposes of the present invention, shaped bodies are solidsubstances which have a predominantly one-dimensional shape, e.g.fibers, a predominantly two-dimensional shape, e.g. films, or athree-dimensional shape, e.g. pellets or injection-molded parts.

Accordingly, advantageous apparatuses for the production of such shapedbodies are a spinning apparatus, an apparatus for producing films, e.g.a film blowing apparatus or a film drawing apparatus, or a granulator.It is also possible for a plurality of identical or different machinesof this type to be connected to the piping system b).

Such apparatuses and processes for producing the respective shapedbodies are known per se, for example melt spinning units and blowingshafts from Fourné, loc cit, pages 273-368, apparatuses for filmproduction from WO 98/5716, WO 98/24324 or EP-A-870 604 and granulators,preferably underwater granulators or underwater pressure granulators,from German patent application number 10037030.6.

1. An apparatus suitable for producing shaped bodies comprisingthermoplastic polymers from monomers which form such polymers in a batchprocess, comprising a) at least one reactor suitable for the batchwisepreparation of a melt of a thermoplastic polymer from monomers whichform such a polymer, b) a piping system suitable as circulation line forthe melt of the thermoplastic polymer and c) at least one apparatussuitable for the production of shaped bodies from the melt of athermoplastic polymer, wherein the reactor or reactors a) is/areconnected to the piping system b) and the apparatus or apparatuses c)is/are connected to the piping system b).
 2. An apparatus as claimed inclaim 1, wherein the reactor or reactors used in a) is/are suitable forthe reaction at a pressure in the range from 0 to 3 MPa and at atemperature in the range from 100 to 380_C.
 3. An apparatus as claimedin claim 1, wherein the piping system b) additionally has a conveyingdevice suitable for moving the melt of the thermoplastic polymer in thelongitudinal direction of the piping system.
 4. An apparatus as claimedin claim 1, wherein a granulator is used as apparatus c).
 5. Anapparatus as claimed in claim 1, wherein a spinning apparatus is used asapparatus c).
 6. An apparatus as claimed in claim 1, wherein anapparatus for producing a film is used as apparatus c).
 7. An apparatusas claimed in claim 1, wherein the mean average pipe diameter in thepiping system b) between the first reactor a) and the last apparatus c)viewed in the flow direction is equal to or greater than the meanaverage pipe diameter between the last apparatus c) and the firstreactor a) viewed in the flow direction.
 8. An apparatus as claimed inclaim 1, wherein the ratio of the mean average pipe diameter in thepiping system b) between the first reactor a) and the last apparatus c)viewed in the flow direction to the mean average pipe diameter betweenthe last apparatus c) and the first reactor a) viewed in the flowdirection is in the range from 1:1 to 10:1.
 9. An apparatus forproducing shaped bodies comprising thermoplastic polymers from monomerswhich form such polymers in a batch process in an apparatus as claimedin claim 1, which comprises a) preparing a melt of a thermoplasticpolymer batchwise from monomers which form such a polymer in at leastone reactor, b) feeding the melt of the thermoplastic polymer obtainedin step a) into a piping system suitable as circulation line for themelt of the thermoplastic polymer and moving it through the pipingsystem at a mean average wall shear rate in the range from 0.1 to 100s-¹ and a mean average flow velocity in the range from 0.1 to 100 cm/s,c) taking the melt of the thermoplastic polymer from the piping systemb) and producing shaped bodies from the thermoplastic polymer.
 10. Aprocess as claimed in claim 9, wherein monomers selected from the groupconsisting of adipic acid, hexamethylenediamine, terephthalic acid,xylylenediamine, hexamethylenediammonium adipate, caprolactam andmixtures thereof are used in step a).
 11. A process as claimed in claim9, wherein hexamethylenediammonium adipate is used as monomer in stepa).
 12. A process as claimed in claim 9, wherein the temperature of themelt of the thermoplastic polymer in the piping system used in step b)is from 0 to 60_C above the melting point of the thermoplastic polymerdetermined in accordance with ISO 11357-1 and 11357-3.
 13. A process asclaimed in claim 1, wherein, in step c), melt of the thermoplasticpolymer is taken continuously from the piping system.